This invention relates to a fastener for securing a circuit board to a chassis or another circuit board of an electronic appliance in a spaced relationship by a predetermined fixed distance from each other.
Electronic appliances often employ means for securing a circuit board to a chassis or another circuit board in a spaced relationship by a predetermined fixed distance from each other. FIG. 1 shows an exemplary one of such means wherein a hollow tubular member a is interposed between a circuit board A and a chassis B and a bolt b is fitted in and extends through the hollow of the tubular member a and fastens the circuit board A and the chassis B to each other with a nut c screwed thereon. Another exemplary means is shown in FIG. 2 wherein a hollow tubular member a is interposed between a circuit board A and a chassis B and a pair of bolts b are screwed into the opposite end portions of a threaded hollow of the tubular member a to fasten the circuit board A and the chassis B to each other. The two means described above commonly have a drawback that, since the head d of the bolt b or each of the bolts b is projected to the outside of the circuit board A, the head d frequently contacts with some part on the circuit board A to cause short-circuiting. The means also have a common drawback that much time is required for assembly using the same. Such a means as shown in FIG. 3 is also conventionally employed wherein a head d of such a bolt as described above is accommodated in an accommodating member e so as not to be projected to the outside of a circuit board A. The means, however, has drawbacks that such an accommodating member e for accommodating the head d of a bolt is required in addition to a hollow tubular member a and that a step of producing the accommodating member e is additionally required, resulting in increase in production cost.
Recently, such an isolating fastener as shown in FIG. 4 has been proposed and is now in practical use. A fastener of the type shown is superior to the conventional isolating members described above in that the production cost is comparatively low because it is formed by integral molding of a synthetic resin material and that a circuit board A can be secured to a chassis B in a spaced relationship by a predetermined fixed distance only by fitting the opposite end portions of the fastener into perforations in the circuit board A and the chassis B, and accordingly the operation efficiency is high. With the fastener of the type described just above, fixation of the same to the circuit board A only makes use of resiliency of fixing fingers h which are provided at the top of the fastener and normally resiliently urged outwardly or upwardly from the position shown in FIG. 4 while fixation to the chassis B is attained by a wing band g and a plurality of contact elements i provided at lower portions of the fastener. Accordingly, the fastener has a drawback that it cannot stand use for a long period of time and it is particularly unsuitable for use with an electronic appliance of an aircraft or a car.